Two Mutations Commonly Associated with Daptomycin Resistance in Enterococcus faecium LiaST120A and LiaRW73C Appear To Function Epistatically in LiaFSR Signaling.

The cyclic antimicrobial lipopeptide daptomycin is now frequently used as a first-line therapy in serious infections caused by multidrug-resistant Enterococcus faecium. Resistance to daptomycin in E. faecium is mediated by activation of the LiaFSR membrane stress response pathway. Deletion of liaR, encoding the response regulator of the system, restores susceptibility to daptomycin, suggesting that the LiaFSR pathway is a potential target for the development of drugs that would induce hypersusceptibility to daptomycin and make it more difficult for enterococci to become daptomycin-resistant. In clinical isolates of E. faecium, substitutions in the membrane-bound histidine kinase LiaS (T120A) and its response regulator LiaR (W73C) are found together, suggesting a potential epistatic relationship in daptomycin resistance. Using in vitro phosphorylation studies, we show that while the phosphotransfer rate of wild-type LiaS and LiaST120A to either wild-type LiaR or LiaRW73C remains rapid and comparable, the LiaS-dependent dephosphorylation rate of phosphorylated LiaRW73C is markedly higher. When the two adaptive mutants LiaRW73C and LiaST210A are paired, however, LiaS-mediated LiaR dephosphorylation is restored back to wild-type levels. Taken together with earlier work showing that LiaRW73C leads to an increased level of oligomerization and subsequently favors an increased level of transcription of the LiaFSR regulon, the net effect of the two commonly found LiaST120A and LiaRW73C alleles would be to coordinately increase the strength and persistence of LiaFSR signaling and decrease daptomycin susceptibility. The in vitro approaches developed in this work also provide the basis for screens for identifying drug candidates that inhibit the LiaFSR pathway.

The Role of Vitamin D Levels in Optimizing Treatment for Pediatric Inflammatory Bowel Disease (IBD) Patients and an Examination Into Different Factors That Influence IBD Treatment Outcomes.

Background Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), presents significant challenges, particularly in pediatric patients. Vitamin D deficiency has been associated with IBD, but its role in disease activity and remission remains unclear. This study investigates the relationship between serum vitamin D levels and IBD markers, including Pediatric Crohn's Disease Activity Index (PCDAI), Pediatric Ulcerative Colitis Activity Index (PUCAI), fecal calprotectin levels, and endoscopy findings. It also explores racial and ethnic disparities in these relationships. Methodology A retrospective study was conducted involving 51 pediatric patients with IBD from the Nemours Children's Health EMR system. Inclusion criteria required documented serum vitamin D levels at diagnosis and post-treatment, and at least one post-treatment assessment of PUCAI/PCDAI, calprotectin, or endoscopy. The study employed Spearman and Pearson correlation tests to analyze the associations between vitamin D levels and IBD markers. Ethnicity and race were analyzed using t-tests and chi-square tests. Results No statistically significant correlations were found between changes in serum vitamin D levels and IBD markers (endoscopy results, calprotectin levels, PUCAI/PCDAI scores) for both UC and CD. Analysis of racial and ethnic disparities revealed that Hispanic patients had significantly higher post-treatment calprotectin levels compared to non-Hispanics, although other markers showed no significant differences. Vitamin D levels did not significantly differ between racial or ethnic groups. Conclusions This study found no significant correlation between serum vitamin D levels and IBD activity markers in pediatric patients. Despite initial hypotheses, vitamin D levels do not appear to be useful in assessing IBD remission or disease state. Racial and ethnic disparities in IBD severity were observed, but further research with larger sample sizes and more consistent data collection is needed to draw more definitive conclusions.

Cerebellar growth, volume and diffusivity in children cooled for neonatal encephalopathy without cerebral palsy.

Children cooled for HIE and who did not develop cerebral palsy (CP) still underperform at early school age in motor and cognitive domains and have altered supra-tentorial brain volumes and white matter connectivity. We obtained T1-weighted and diffusion-weighted MRI, motor (MABC-2) and cognitive (WISC-IV) scores from children aged 6-8 years who were cooled for HIE secondary to perinatal asphyxia without CP (cases), and controls matched for age, sex, and socioeconomic status. In 35 case children, we measured cerebellar growth from infancy (age 4-15 days after birth) to childhood. In childhood, cerebellar volumes were measured in 26 cases and 23 controls. Diffusion properties (mean diffusivity, MD and fractional anisotropy, FA) were calculated in 24 cases and 19 controls, in 9 cerebellar regions. Cases with FSIQ ≤ 85 had reduced growth of cerebellar width compared to those with FSIQ > 85 (p = 0.0005). Regional cerebellar volumes were smaller in cases compared to controls (p < 0.05); these differences were not significant when normalised to total brain volume. There were no case-control differences in MD or FA. Interposed nucleus volume was more strongly associated with IQ in cases than in controls (p = 0.0196). Other associations with developmental outcome did not differ between cases and controls.